1. Field of the Invention
This invention relates generally to the field of digital interface design and, more particularly, to communications interface design.
2. Description of the Related Art
Within the past two decades personal computers (PC) have joined television sets, high fidelity stereo equipment, and compact disc players as part of the vast array of electronic devices widely used in both the office and the home. In recent years the electronics marketplace has also seen a proliferation of appliances and personal electronics devices that use solid-state memory, in addition to devices that employ other widely used storage mediums. Some of the more popular devices include video cameras, photo cameras, personal digital assistants, portable music devices, and consumer electronics systems such as set top boxes, high definition (HD) television systems and digital recorders among others. Corresponding to the proliferation of such devices has been an emphasis on connectivity and networking for transferring data between the personal electronic devices, personal computers, and/or set top boxes.
In addition to specifications for internal busses, such as the Peripheral Component Interconnect (PCI), various interface standards for connecting computers and external peripherals have also been introduced, each aiming to provide simple connectivity at high speeds. Examples of such standards include the IEEE 1394 standard also referred to as FireWire, and the Universal Serial Bus (USB), both high-speed serial bus protocols. The most widely used networking standard for connecting computers in both Local Area Networks (LANs) and Wide Area Networks (WANs) has been the Ethernet protocol. More specifically, Ethernet is the IEEE 802.3 series standard, originally based on the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) method that provided a means for two or more computer stations to share a common cabling system. CSM/CD has formed the basis for Ethernet systems that reached transfer speeds in the megabit range, that is the Mbit/sec range. Recent switched based and/or router based Ethernet systems are capable of supporting transfer rates in the Gbit/sec range. Ethernet generally makes efficient use of shared resources, is typically easy to reconfigure and maintain, and provides compatibility across many manufacturers and systems, while keeping the cost low.
However, Audio/Video (A/V) consumer entertainment systems such as HD televisions, set-top box and personal video recorders (PVRs) are generally not optimized for distributing/receiving high quality high resolution programming content through a standards based Ethernet network. This typically holds for broadband Ethernet connections as well. One issue that has presented a problem in the development of entertainment systems has been the migration from a closed network to an open network while maintaining performance levels required in the distribution of higher quality/resolution A/V programming content. It has also become increasingly difficult, if at all possible, to obtain the desired performance levels while moving real-time streaming data over a limited bandwidth local bus, utilizing standard Ethernet controllers. In addition, the generally high prices of consumer electronic products featuring Ethernet network components have made it difficult to assemble systems at reasonable costs.
Certain complexities inherent in the transmission of real-time and non-real-time audio/video data do not present a problem when employing data transport models and/or approaches such as digital satellite, cable, and terrestrial and proprietary transmission systems. Digital satellite, cable and other proprietary transmission systems are typically “closed networks”. Generally, a “closed network” in this context refers to a standard or non-standard (proprietary) solution not available to the general public. A proprietary solution will typically afford an individual manufacturer or group of manufacturers the time and resources to develop unique solutions that may achieve the desired performance goals, but such solutions will not usually interoperate with competing products. Examples of proprietary solutions typically include digital video broadcasting through Cable TV (CATV) Networks, digital video broadcasting over Public Switched Telephone Network (PSTN) and/or Integrated Services Digital Network (ISDN), and digital video broadcasting through Satellite Master Antenna TV (SMATV) distribution system networks. A variety of network standards have been defined for various physical and transport models, and implemented under standards bodies, such as the DVB—ETSI (European Telecommunications Standards Institute), for example. The overall content distribution system is typically controlled by broadband network providers such as Cable Vision, Comcast and Direct TV. A broadband network provider typically dictates the hardware, software and protocols used in such a system.
The diagram in FIG. 1 illustrates an example of a closed network implementing an interactive pay-per-view system reference model. The broadcast channel 102 is usually a unidirectional broadband network that distributes video, audio and possibly data to customer sites 104. The Interaction channel 106 is typically a bi-directional channel established between the user 104 and service provider 108 for interaction purposes. Interaction channel 106 generally comprises a narrowband channel, commonly known as a return channel, which may be used to make requests to the service provider or to answer questions. The broadcast head-end 110 and Interactive head-end 112 bridge the video and audio broadcast channels 102 to the Broadcast and interactive Service provider 108, usually over a proprietary network. On the Customer premise 104 side, connections are typically made to a display device 120 (for example a TV set) through coaxial cabling from a set-top-box 122. The diagram in FIG. 1 shows multiple set-top-boxes within one home. Signals entering the home through a single coaxial cable may be distributed using splitters and possibly repeaters. It is important to note that closed systems or networks have stringent resource provisioning since the end-to-end connection is typically controlled and maintained by a single service provider.
In contrast, in an “open” network the hardware, software and the corresponding protocols are all defined by well-known standards with solutions readily available from different manufacturers, where such solutions are generally interoperable with each other. Additionally, an open network is a shared network, with potentially numerous service and content providers using the shared network to distribute content. An example of an open network is the Internet as defined by the Internet Engineering Task Force (IETF). The IETF is a large, open community of network designers, operators, vendors, and researchers whose purpose is to coordinate the operation, management and evolution of the Internet, and to resolve short-range and mid-range protocol and architectural issues. Open network protocols are layered, based on the International Standards Organization (ISO) networking model. Any given open network generally has additional overhead depending on the network protocols used while communicating through the open network. Many, if not all current solutions do not have the system resources to support an open network model while processing higher quality and resolution A/V programming content. In addition, resource provisioning is typically more difficult to manage on such open networks.
Historically, broadband A/V distribution has been performed by satellite and cable services utilizing set-top-box (STB) and PVR devices. An example of such a system is shown in FIG. 2. The diagram in FIG. 3 describes the broadband distribution flow—as relating to the system architecture shown in FIG. 2—of an A/V channel from satellite, cable or terrestrial reception to a rendering device, which may be a High Definition TV (HDTV) set or video projector. For example, referring to the components in FIG. 2 and the flow illustrated in FIG. 3, a satellite dish may receive various broadcast channels as satellite signals (301). The receiver (Front End Device) may be a zero IF tuner 202 implementing quadrature phase shift keying (QPSK) or phase shift keying (PSK) demodulation along with forward error correction (FEC) (302). The broadcast video, typically represented in the form of a serial or parallel digital output conforming to a standard interface such as digital video broadcast server (DVBS) or DirecTV specification, may be transferred through the Transport Stream Interface (TSI) 204, (304). TSI 204 typically comprises a dedicated bus configured for transferring digital audio and/or video data packets, oftentimes in real-time. In another set of applications, TSI 204 may be a dedicated bus configured for transferring real-time application data in general.
Details of a standard TSI are documented in the CENELEC (European Committee for Electro-Technical Standardization) Standards body specification EN 50083-9. More specifically, reference information pertaining to the aforementioned standard TSI is contained in ‘EN 50083-9:1998 “Cable networks for television signals, sound signals and interactive services—Part 9: Interfaces for CATV/SMATV head ends and similar professional equipment for DVB/MPEG-2 transport streams”’, as well as in ‘EN 50083-9:2002 “Cable networks for television signals, sound signals and interactive services—Part 9: Interfaces for CATV/SMATV head ends and similar professional equipment for DVB/MPEG-2 transport streams”’. The specification may be obtained from the following webpage: http://www.cenelec.org/Cenelec/Homepage.htm.
Referring again to FIG. 3 in relation to FIG. 2, the data may then be parsed (306), descrambled (308) and further de-multiplexed (310) depending on the conditional access methods and compression standards that have been implemented. The Data may then be stored (312) for use on another system or for playback at a later time, or may be decoded (314) and played back on a rendering device (316). It should be noted that many of the steps outlined in FIG. 3 are typically implemented in both hardware and software. Decoding (314) and de-multiplexing (310) are examples of functions that can be performed by hardware and software. Constantly changing standards and methods oftentimes necessitate the implementation of certain functions in software. Implementing these algorithms in software will generally afford the highest degree of flexibility while minimizing obsolescence.
The above-described distribution model generally works well for satellite, cable or terrestrial broadcasting. However, distribution of A/V content using Ethernet as the primary method of distribution produces additional challenges. As shown in FIG. 2, an Ethernet controller 210 is typically coupled to a local (or memory) bus 212 of the STB/PVR system on a chip (SOC) 208. This network connection has been traditionally used for Internet access through cable modems or digital subscriber line (DSL) broadband connections. Using standard Ethernet controllers on a local bus will generally not deliver the performance required for real time A/V distribution. Because the Ethernet controller 210 generally shares the local bus 212 with other peripherals, processing of network data may be considerably slowed down and/or delayed. Processing additional network protocols, such as TCP/IP and others, may further slow down the system.
Existing A/V solutions generally use Ethernet connectivity at typical data rates of 1 to 6 Mbits per second for activities such as Internet web surfing, and as a return path for video-on-demand (VOD) applications, billing systems, and limited A/V distribution in the home. Bandwidth requirements for streaming higher quality video and/or audio content are substantially higher. For example, to support one High Definition (HD) video stream, a throughput of 12 to 60 Mbits per second with possibly some form of priority bandwidth provisioning, including QOS (Quality of Service), may be required. The need for QOS is usually determined by buffering and latency. For example, increased bandwidth requirements may necessitate an increased QOS in case a time delay between switching video content channels exceeds the average acceptable time elapsed between channel selections made by a user while “channel surfing”, due to buffering delays. Distribution of A/V data must preferably remain steady with minimal delays. With existing Ethernet solutions, similar to Ethernet controller 210 in FIG. 2, achieving the required performance levels is typically very difficult if at all possible.
In addition, STB and other consumer electronics devices are generally very cost sensitive. Most embedded processors and hardware building blocks comprised in the bulk of consumer electronics devices are usually low cost and feature limited performance (typically referenced as millions of instructions per second (MIPS)). Trade-offs between memory access speeds, CPU speed, and power consumption are quite common. For most system designers, migrating to an open network with its additional network processing overhead, when the CPU bandwidth is just enough for the core application, might necessitate migrating to a more expensive system solution. In addition, with this additional network overhead, utilizing a standard Ethernet controller will typically not give the performance needed to enable an open network solution, especially when aiming for low cost consumer electronics products.
The concept of transferring real-time and non real-time video and audio content over a shared and open network has been addressed in a variety of ways. For example, wireless modulation solutions such as 801.11a, b and g have been considered for shared access local area networks. Wired solutions such as 802.3 10/100/1000 Base-T twisted wire pair encoding solutions have also been considered. Numerous solutions have also been described at the media access and transport level. Some of these solutions include methods of media access using Ethernet 802.3, Wireless, 802.11a,b and g and other solutions such as Asynchronous Transfer Mode (ATM), Synchronous Optical Networking (SONET), and others. Additionally, various methods to achieve a higher QOS have been addressed by certain proprietary solutions.
One approach involves the concept of “transmission profiles”, where network systems and aggregators select paths by detecting additional information in the network packet, as in an Ethernet packet. In other cases Virtual Local Area Network (VLAN) tags are utilized, or ATM is implemented utilizing (virtual) path identifiers. Some solutions implement data bandwidth allocation, where network systems may be architected such that high-speed access is provided over frequency-division multiplexed (FDM) channels, enabling transmission of Ethernet frames and/or other data across a cable transmission network or other form of FDM transport. Devices would typically allocate downstream and upstream bandwidth on previously defined frequency channels based on time slot assignments for various network packets. In terms of transport, many current solutions utilize the Internet Protocol (IP). In some cases, various connection-oriented protocols such as Transmission Control Protocol (TCP) are employed.
One example of a productized solution is the TF-530 “Digital Streaming Controller” by Taifatech Inc. The TF-530 is a bridging engine, bundled with a TCP/IP protocol and featuring an integrated RISC CPU with various software components, including TCP/IP protocol stack and HTTP server applications. The software also includes IP, User Datagram Protocol (UDP), TCP, Internet Control Message Protocol (ICMP) and Real-time Transport Protocol (RTP) accelerator support. The TF-530 also features a dedicated streaming video interface.
However, most existing systems typically do not offer an open network solution built around the Ethernet protocol that is capable of maintaining performance levels required in the distribution of higher quality and resolution A/V programming content. Current systems utilizing standard Ethernet controllers generally do not allow for movement of real time streaming data over a limited bandwidth local bus, thus failing to achieve desired performance levels.
Other corresponding issues related to the prior art will become apparent to one skilled in the art after comparing such prior art with the present invention as described herein.